Color Measurement on Very Small Samples - AN-1003

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When product is in short supply or is very expensive, it is important to use the smallest amount of sample possible for color measurement. This application note describes HunterLab’s color measurement solutions for consistently reading very small amounts of solids, powders, and liquids.

Challenge: To measure small-to-micro samples with precision.

In some applications, samples may be rare, very valuable or in short supply, typically in quantities from small-to-micro. The consistent color measurement of small samples is possible with special accessories. Development of a repeatable measurement method is essential for color discrimination in these small samples. Consideration should be given to an appropriate instrument, color scale, illuminant, observer and special sample holder, if necessary.

Measurement Solutions for Solids in Reflectance Mode

In the case of a solid sample, the port opening must be reduced to allow for viewing of the sample without a background. Many HunterLab instruments have the ability to switch from the normal LAV - Large Area of View to an SAV - Small Area of View by a motorized. When placing the sample for measurement, the retroviewer option is used to ensure that the desired sample area completely covers the opening in the port plate. This means that the sample size must be equal to or slightly larger than the 4 mm or 3 mm openings. In addition to lining up the sample correctly, the change of geometry with this option will cause a slight shift in the color values of the calibration standards.

Measurement Solutions for Powders in Reflectance Mode

For small quantities of powder, HunterLab has designed a special modified port plate for reflectance measurements of approximately 0.4 cc of packed powder. The sample is s scooped into the powder holder and packed down with a plunger. The powder holder is then placed in a specially-designed port plate and the powder measured through the holder’s clear window.

References

Hunter, Richard S., and Harold, Richard W., The Measurement of Appearance, 2nd Ed., John Wiley and Sons, Inc. New York, NY USA 1987.

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